The present invention relates to a process of producing hydrogen peroxide by direct reaction between hydrogen and oxygen in the presence of a catalyst to form hydrogen peroxide gas.
Production of hydrogen peroxide by direct reaction between hydrogen and oxygen can be performed by contacting hydrogen and oxygen with a catalyst in an aqueous reaction medium as described in, for example, U.S. Pat. Nos. 4,661,337, 4,681,751, 4,772,458, 5,180,573, 5,128,114 and 5,338,531, as well as J. R. Kosak (DuPont), "A Novel Fixed Bed Catalyst for the Direct Combination of H.sub.2 and O.sub.2 to H.sub.2 O.sub.2 ", Chem. Ind. (Dekker), 1995, Vol, 62, Catalysis of Organic Reactions.
However, the formation of hydrogen peroxide in these processes is rather slow. Further, it is hard to obtain high concentrations of hydrogen peroxide and the product will also contain additives in the reaction medium as impurities, such as sulfuric acid and/or bromide or chloride ions. These problems are assumed to be due to the facts that only low amounts of the reactants can be dissolved in the reaction medium and that the same catalyst that promotes formation of hydrogen peroxide also catalyses direct formation of water and peroxide decomposition into water and oxygen.
A similar process conducted in an organic solvent as reaction medium is described in WO 97/32811. However, in order to obtain hydrogen peroxide in aqueous solution a separation step such extraction or desorption is necessary.
DE patent 558431, CH patent 140403, U.S. Pat. No. 2,368,640 and WO 97/32812 disclose production of hydrogen peroxide from hydrogen and oxygen in gas phase. However, unless operating under extreme conditions the selectivity is low: instead of hydrogen peroxide a great deal of the end product will be water.
U.S. Pat. No. 5,500,202 discloses production of hydrogen peroxide in a reactor, wherein hydrogen and oxygen are reacted in a gaseous state at the surface of a solid catalyst and the hydrogen peroxide formed is dissolved in a liquid trickling through the reactor. However, also in this process only hydrogen peroxide solutions of low concentration and low purity can be obtained.